A hard-disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on one or more circular disks having magnetic surfaces. When an HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read/write head that is positioned over a specific location of a disk by an actuator. A read/write head uses a magnetic field to read data from and write data to the surface of a magnetic-recording disk. Write heads make use of the electricity flowing through a coil, which produces a magnetic field. Electrical pulses are sent to the write head, with different patterns of positive and negative currents. The current in the coil of the write head induces a magnetic field across the gap between the head and the magnetic disk, which in turn magnetizes a small area on the recording medium.
Increasing areal density (a measure of the quantity of information bits that can be stored on a given area of disk surface) is one of the ever-present goals of hard disk drive design evolution. In turn, as recording tracks in HDDs become narrower and narrower and bits are recorded smaller and smaller, there is a need to raise the recording magnetic field strength to improve the recording capabilities correspondingly. However, as the recording magnetic field strength is raised the probability of the magnetic field leaking outside of a desired recording track likewise increases. This is an undesirable situation because a strong magnetic field leakage can cause ATI (“Adjacent Track Interference”) to tracks immediately adjacent to the desired track, or FTI (“Far Track Interference”) to tracks more than a track away from the desired track. Either scenario, ATI or FTI, is likely to cause data disappearance of or corruption to the adjacent or far track, thus causing read errors. Thus, the manner in which ATI and/or FTI is managed and inhibited is an important factor in improving the performance of HDDs.
Any approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.